Generally, the structure of a common flat panel liquid crystal display (LCD) device includes a backlight module, a polarizer, a TFT liquid crystal display module, a color filter, an analyzer, and so on. Nevertheless, by the technology available today, the overall light energy usage of those conventional flat panel LCD devices can only achieve about 3-6% so that there is a very severe energy loss. In detail, it is the color filter that causes the most energy loss, in which there can be about 70% of light shining therethrough is wasted. In another word, the light efficiency of those conventional color filters is only about 30%. In addition, the waste caused by the polarizer can achieve as high as 60% which is another factor causing sever energy waste in conventional flat panel LCD devices.
Therefore, researchers all over the world are working tirelessly to come up with all kinds of new techniques for enhancing the LCD device's power saving efficiency effectively.
One such study is an optical element disclosed in U.S. Pat. No. 6,867,828, entitled “Light guide apparatus, a backlight apparatus and a liquid crystal display apparatus”, and U.S. Pat. No. 7,164,454, entitles “Color filterless display device, optical element and manufacture”, which is substantially a color separation element, being a micro-prism array of specific angle design or a micro-grating array, capable of separating and far-field diffracting a white light beam into a red, a green and a blue light beam. However, because of its complicity, the manufacturing process of the aforesaid optical element is so complex that not only its yield is poor, but also it has comparatively high cost. In addition, the resulting red, green and blue light beams are being discharged according to the diffraction angle of the optical element in a scattering manner and will keep scattering even when traveling in a display panel, causing flare and ghost image on the display panel, so that the aforesaid optical element is not performed well as it is applied in display panels. Moreover, the techniques in the aforesaid U.S. patents provide no way of enhancing aperture ratio and polarization efficiency.
Another such study is disclosed in a paper, entitled “Design of hybrid grating for color filter application in liquid crystal display”, by Mr. Hui-Hsiunng Lin, at “The Joint Conference on Plastic Optical Fiber & Microoptics 2006”, hosted by “Korea POF Communication Forum”, in which a double-sided lenticular lens array having dual triangle-shaped microstructures formed thereon in a periodic manner is provided. The aforesaid double-sided lenticular lens array is able to collimate an incident while light for allowing the same to be separated into a red, a green and a blue light which are to be collimated thereafter, using which the shortcoming of conventional grating that it is restricted to operate on parallel incident light can be overcome, and also the poor sensitivity affected by the longitudinal and transverse errors caused in the optical element assembly is avoided.
Generally, a beam is composed of a vertical S-polarized beam and a horizontal P-polarized beam in fifty-fifty, according to which those conventional liquid crystal display devices usually has a polarizer to be disposed between its backlight module and liquid crystal display panel for allowing only one (S-polarized) of the two polarized beam to pass therethrough while absorbing the other (P-polarized). Thus, as the color separation grating design used in the aforesaid paper is adapted for common light beam that it did not take the polarization characteristic into consideration, the light loss ratio could be as high as 50%.